1. Field of the Invention
With the aging of society in recent years, there is an increase in the number of bedridden persons, and attention has been directed to the method of conducting diagnosis based on variations in the heart rate as measured by an electrocardiograph as a method of monitoring the physical condition of the bedridden elderly person. Presently, with growing awareness of health management, people have become more desirous of readily measuring the heart rate during sleep in the ordinary family.
2. Description of the Related Art
However, when the conventional electrocardiograph is to be used for measuring the heart rate, there is a need to affix a plurality of electrodes directly to the skin, and the conventional device therefore has the drawback that the person to be checked is held restrained for a prolonged period of time by the cords extending from the electrodes to the main body of the instrument. Because of the same situation involved in measuring the respiration rate, difficulty is encountered in making the measurement easily in the home.
Accordingly, systems are known for measuring the dynamic conditions of patients using a capacitance-type sensor [(i) Tomohiro Ohkubo and Yoshimichi Yonezawa, “System for Measuring Dynamic Conditions of Patients by Capacitance-Type Sensor,” Medical Electronics and Biomedical Engineering, 32-2, 132/135, 1994, (ii) Takeshi Minamiura, Yoshihisa Fujiwara, Hidetaka Sakai, Hidefumi Matsuura and Shoji Yasuda, “Development of Portable Nonrestraint Sleep Sensor,” Society of Electronics, Information and Communications, 2002 General Meeting, Abstracts, D-7-25).
Although the heart rate or respiration rate of patients can be measured by such a sensor free of restraint, the sensor still remains to be improved with respect to the sensitivity of measurement.